By adjusting preparation procedures and structural elements, the component under test attained a coupling efficiency of 67.52% and an insertion loss of 0.52 decibels. To the best of our understanding, a tellurite-fiber-based side-pump coupler has, to our knowledge, never been developed before this instance. The incorporation of this fused coupler will render mid-infrared fiber lasers and amplifiers considerably more straightforward to design and fabricate.

This paper proposes a joint signal processing scheme, comprising a subband multiple-mode full permutation carrierless amplitude phase modulation (SMMP-CAP), a signal-to-noise ratio weighted detector (SNR-WD), and a multi-channel decision feedback equalizer (MC-DFE), to address bandwidth limitations in high-speed, long-reach underwater wireless optical communication (UWOC) systems. The SMMP-CAP scheme's approach to trellis coded modulation (TCM) subset division is to partition the 16 quadrature amplitude modulation (QAM) mapping set into four 4-QAM mapping subsets. An SNR-WD and an MC-DFE are employed to strengthen the system's demodulation capabilities within a fading channel. A laboratory experiment revealed that -327 dBm, -313 dBm, and -255 dBm are the minimal received optical powers (ROPs) needed for data rates of 480 Mbps, 600 Mbps, and 720 Mbps, respectively, when utilizing a 38010-3 hard-decision forward error correction (HD-FEC) threshold. Moreover, the system effectively achieved a data transmission rate of 560 Mbps in a swimming pool with a transmission length extending up to 90 meters, accompanied by a total attenuation value of 5464dB. We believe that this is the first instance of a high-speed, long-distance UWOC system, constructed and demonstrated using the SMMP-CAP methodology.

In in-band full-duplex (IBFD) transmission systems, signal leakage from a local transmitter results in self-interference (SI), which can severely distort the receiving signal of interest (SOI). The SI signal is completely canceled via the superposition of a local reference signal having the same strength but a reversed phase. Medical nurse practitioners Even though the reference signal is generally manipulated manually, this can be a significant impediment to achieving high-speed and high-accuracy cancellation. A real-time adaptive optical signal interference cancellation (RTA-OSIC) scheme, leveraging a SARSA reinforcement learning (RL) algorithm, is proposed and experimentally demonstrated to surmount this challenge. The RTA-OSIC scheme, leveraging an adaptive feedback signal generated from evaluating the received SOI quality, can autonomously regulate the amplitude and phase of a reference signal using a variable optical attenuator (VOA) and a variable optical delay line (VODL). An experiment involving a 5GHz 16QAM OFDM IBFD transmission is conducted to validate the proposed system's feasibility. The suggested RTA-OSIC scheme, when applied to an SOI operating across three bandwidths (200MHz, 400MHz, and 800MHz), permits the adaptive and accurate recovery of the signal within eight time periods (TPs), the standard duration for a single adaptive control step. With an 800MHz bandwidth, the SOI achieves a cancellation depth measurement of 2018dB. tick endosymbionts The stability of the proposed RTA-OSIC scheme is assessed, considering both its short-term and long-term performance. In future IBFD transmission systems, the proposed approach, according to the experimental results, appears to be a promising solution for achieving real-time adaptive SI cancellation.

The operation of electromagnetic and photonics systems hinges on the active participation of active devices. Integration of the epsilon-near-zero (ENZ) effect with a low Q-factor resonant metasurface is commonly employed to fabricate active devices, yielding a substantial enhancement of light-matter interaction at the nanoscale. Nevertheless, the limited Q-factor resonance could hinder the optical modulation. Optical modulation in low-loss, high-Q-factor metasurfaces has received comparatively less attention. An effective method for producing high Q-factor resonators has recently been established by the emergence of optical bound states in the continuum (BICs). This study numerically confirms the creation of a tunable quasi-BICs (QBICs) structure through the integration of a silicon metasurface with an ENZ ITO thin film. DCycloserine A unit cell containing five square holes within the metasurface design; the pivotal position of the central hole influences the generation of multiple BICs. Through the application of multipole decomposition and the evaluation of near-field distribution, we also elucidate the nature of these QBICs. Active control of the resonant peak position and intensity in the transmission spectrum is shown by integrating ENZ ITO thin films with QBICs on silicon metasurfaces. This is due to the notable tunability of ITO's permittivity via external bias and the high Q-factor enabled by QBICs. QBICs consistently display remarkable effectiveness in modulating the optical reaction of such hybrid architectures. The upper limit for modulation depth is fixed at 148 decibels. We also scrutinize the effect of ITO film carrier density upon near-field trapping and far-field scattering and its consequential effect on the performance of the optical modulation device employing this particular structural arrangement. Our results have the potential to find promising applications within the burgeoning field of active high-performance optical devices.

Our proposal for long-haul, coupled multi-core fiber transmission includes a fractionally spaced, frequency-domain, adaptive multi-input multi-output (MIMO) filter for mode demultiplexing. The input signal's sampling rate remains below twofold oversampling, using a non-integer oversampling factor. Subsequent to the fractionally spaced frequency-domain MIMO filter, frequency-domain sampling rate conversion to the symbol rate, i.e., one sampling, is implemented. Deep unfolding dictates the adaptive control of filter coefficients via stochastic gradient descent and gradient calculation, using backpropagation across the sampling rate conversion of output signals. Our assessment of the proposed filter relied on a long-haul transmission experiment using 16 channels of wavelength-division multiplexed, 4-core space-division multiplexed 32-Gbaud polarization-division-multiplexed quadrature phase shift keying signals transmitted over coupled 4-core fibers. Despite the 6240-kilometer transmission, the fractional oversampling frequency-domain adaptive 88 filter, operating at 9/8 oversampling, incurred a minimal performance penalty compared to the standard 2 oversampling frequency-domain adaptive 88 filter. Computational complexity, as determined by the number of complex-valued multiplications, was diminished by a remarkable 407%.

The medical field relies heavily on the usage of endoscopic techniques. Small-diameter endoscopes are built as fiber bundles, or, for improved performance, utilizing graded index lenses. Though fiber bundles can handle mechanical forces during their utilization, the GRIN lens's operational effectiveness can be impacted by its deflection. We delve into the effects of deflection on the quality of the image and accompanying undesirable consequences, examining this in relation to our custom-built eye endoscope. In addition, our efforts to craft a trustworthy model of a bent GRIN lens within the OpticStudio environment are presented here.

Experimental results demonstrate a low-loss RF photonic signal combiner with a uniform frequency response from 1 GHz to 15 GHz and a low group delay variation of 9 picoseconds. A silicon photonics platform, scalable in design, houses the distributed group array photodetector combiner (GAPC), enabling the combination of vast numbers of photonic signals within radio frequency photonic systems.

An optoelectronic oscillator (OEO), characterized by a novel single-loop dispersive design and a broadband chirped fiber Bragg grating (CFBG), is numerically and experimentally studied for chaos generation. Compared to the chaotic dynamics, the CFBG possesses a considerably wider bandwidth, resulting in its dispersion effect outweighing its filtering effect in determining the reflection. Under conditions of guaranteed high feedback strength, the proposed dispersive OEO manifests chaotic dynamics. With the enhancement of feedback strength, a suppression of the characteristic chaotic time-delay signature is witnessed. Grating dispersion directly influences the level of TDS suppression. Our system, without diminishing bandwidth performance, extends the parameter space of chaos, enhances tolerance to modulator bias fluctuations, and improves TDS suppression by at least five times in comparison to the classical OEO design. Experimental results demonstrate a high degree of qualitative concurrence with the numerical simulations. The effectiveness of dispersive OEO technology is evidenced by experimental demonstrations, yielding random bit generation at adjustable rates, up to 160 Gbps.

A novel external cavity feedback structure, based on a double-layer laser diode array with a volume Bragg grating (VBG), is detailed in this paper. A high-power, ultra-narrow linewidth diode laser pumping source, centrally located at 811292 nanometers with a spectral linewidth of 0.0052 nanometers and output exceeding 100 watts, is created by the combination of diode laser collimation and external cavity feedback. The electro-optical conversion efficiencies of the external cavity feedback and collimation are above 90% and 46%, respectively. To modulate the VBG temperature and thereby tune the central wavelength from 811292nm to 811613nm, ensuring complete coverage of the Kr* and Ar* absorption spectra. The first reported instance of an ultra-narrow linewidth diode laser capable of pumping two metastable rare gases is described in this paper.

An ultrasensitive refractive index (RI) sensor, employing the harmonic Vernier effect (HEV) and a cascaded Fabry-Perot interferometer (FPI), is proposed and demonstrated in this paper. By sandwiching a hollow-core fiber (HCF) segment between a lead-in single-mode fiber (SMF) pigtail and a reflective SMF segment, a cascaded FPI structure is formed. The 37-meter offset between the fibers' centers positions the HCF as the sensing FPI, and the reflection SMF segment as the reference FPI.